Well completion method



NOV- 9, 1954 T. o. ALLEN WELL COMPLETION METHOD Filed April 1, 1952INVENTOR. :THOMAS GALLEN, BY s United States Paterrt ice 2,693,856 WELLCOMPLETIONl :METHODll 5 Thomas 0.Allen, Bllaira-Tx.; assignfonbymesn'eSas-L- signments, tof tandardlOlflDevelopment ',C'rnp'ay,

Elizabeth, N. J.; a corporanof :Delaware ApplicationAprila;1952,?seriaiNo.,279,732 10Claims;:^. (Clit 1661-23);

Thefpresent.inventionis'directedtto a'method forcom-l 15 pletin'g foilyandgasfwells. More particularly, the-invention' is directed to Ia methodforcompletin'g oil and gasilwells zin.which-adrilling flu'id'or` mudisfusedto control'the Well. In its more particularaspects, *the-in#`ventionzis. directed `to va methodsfor'completing'anfoil or 20gaswelllinwhich/a column of 'drilling ^mud1is maintainedtf in a casingto control the well.,y

Currentfpractice when. completingl wells',. such as oil andfgasf-wells,through .perforated vcasings isfto have drill# ingvuids', suchasmud,saltrwater',fwater;ior oil,in`fthe`25 wellcasing and to perforate the,casingvwithfbull'e't,lshaped' charge' or punch-type'-perforatorsn Whenvtheupressure'" ofaformation traversed iby- :the vWell "exceeds theIhydrostatic pressure=offacolumn` offoilior waterratthe'completiondepth,l it.' is'lcustomary toiuse weighted-salt .water 30ormormal drilling mud having aradensity: 'great enough to.. exceedformation pressure inz :Order to controlfthe well Vwhile perforating thecasinggand lperformingl otheriV routinecompletion operatiOns.-. lnthefcase :offfawelllf' l'led withl drillingmud-"whenf'thezcasingi'isi'perforated'35 the: drillingtmud flowsintO-:the-rperfdrations'because of the pressure differential existingbetween the interior Ofl thexcasing iandntheformationii'l`hef'perforationsV are therebyipartially orcompletely plugged with mudand'.` this plugging is aggravated by the heat `and instantaneousnt()pressure Vevolved by the "propellannpower in; the fcase-V Ofrbulletperforators and fth'ihigh explosive' -in 'thecasev of the ijett or,shapedl charge perforators'.: Where punch# type' perforators .areemployedfit isivnotxuncomrnonifo'i:VA the drillng'mud'to lose-waterrapidly to :the "formation 45 resultingin. the drilling vmud Vbecomingdehydratedrand: forming plugsr; Datanare `availablewhichrindicatefthatrsuch-plugs awhethe'rfformed bycdehydration' fofl thef fdrill-.i ingmudby heat,and/Orvpressureor"byzlossf'of .watert to the formation areydiiculty towremove hbyffsubsequent"50 cw from-the formation intotthewelll-bore .'-and that-the# productivity of a perforating interval in aproducingyforlmat-ion is rsignicantly reduced.u Fieldcompletion attemptsof wells indicate that such --plugging of--tlre1-perf forationsmaycause' formations `to-be tested v.as"being'-"55 non-productiveandf-thereby condemned-- when y actually the. formation may' t containAeconomically rprodueibleoil or gas.` Thus .itis clear`thatr-theproblemfof. plugging of.perforati0ns isv seriousand isa sourceofl-expense inl-2 well vcompletions, andr Of- -erroneous- -conclusionssin; f ex-f 60 ploratory work 4whichmay cause.- major hydrocarbonne-`serves to remain undiscovered.v

In accordance with my. invention the-,problemof plug ging perforationsin awellcasing in whichacolumnfof, drilling mud 'is maintainedto controla wellis eliminated .65 byproviding in the Welllcasin'g adjacentiaproducingfon. mation a-zone from whichfthedrillingmudtissremovediolexcluded and then -perforating 'inl` said `Zone: 4such that.thedrillingmud' is'not available to plugithe perforations',

The presenti invention. may,. therefore`,. beizbriey ,de'f`l 70 scribedas involvingthe vexclusion from a-Vzonetin a=well"' casing in which acolumn of 'drilling mudis .maintained for ,control of the Well, vthedrilling mud -fro'mgthe zonev while vperforating the casingin"saidwelliInltmyzin vention, the drillin'gimud or'iluid iseXClu'ded'frOm the 75zone vwhere perforation isto` take'place byreplacingfitt witlra fluid,lcharacterized-as :being of'ya 'dens'ity'and/o'r ofa viscosity such ,thatthe `fluid replacing,thedrilling mudaremains in .the zonefto :beperforated unless rc'-V moved :earlier a suHicient'-length of time,atleast-4 hours;` toallow the well :completion iorservicinggoplerations'*toi*k easily removable PLtentedNov. 9, 1954'.V

be completed; includingifpe'rforatil'lg@` therca'sing `in 1 saidremains* in'- said' zone. Thus iny it t will not form drilling mud.

I, therefore, employfin .the izone'in the lcasing'to bei' perforated afluid ofJsuiTcientWeig'ht and/orvl` viscosity plugs intheperforationswhich are 'notf such as Sin the'case of plugs formed by toprevent displacement by heavierfmuds above which* will not plug theperforations orthe formation perforated;4

The fluids that I employ are termed in '-the Oil industryl as gels andmay be described as 'involving heavy metal soaps admixture .withhydrocarbons, such as fuell Oil, crude oil'and lighter fractionsof'fluid petroleum, as-mayv be desired. To provide the-'necessary Weightto the fluid or gel as it maybe termed it may bei desirable to 'admix'intimately with thef gel material, such asv sand 'andthe' like,toprovidethe neces'-y sary weight` thereto. of thefluid replacing thefrom 9 to 18 pounds per gallon.' Of course, the Weight of the uid shouldbe heavier ythan the Weight of th'e drilling mud "in: order to displaceIt is contemplated that the weight drilling fluid should range.Lv

'when formed" a 4 finely `divided i cosity of'the'iluidVreplacing'thedrillingfmud should'L range from about' 10 is also used inthe industry in variousv Ways. ample, gels prepared with 'Napalm andkerosene oil and Weightedrwith For expounds which'have the property of,reverting to a nontO 4000 centipoises atf60FL" I` also contemplateemploying' the 'so-called gel acid 'Whichviscous condition through theaction of chemicals? which" may vbe added during the preparation" or'may'br'eak' automatically With'time orwith adjustmentof tempera# tureand pressure.`

fillv my requirements as setout above.'A For'example Ainacrylates. isupraofmany heavy'fm'etal'soaps lwhich may be-*used in they formation"of "such" gels? formations with which they 'mayfcome 'into 1 contact.

Infaccordance 'yvith-myinvention', 'I prevent the aforementioned"plugging fof 'fperfor'ati'ons and/or formations v French 'Pate'nt'Nof987,352, grantedI April 11, 1951, sets out in detail manyfluids'whichwill by placinga'Weighted'jellylike materialin the wellcasing vor 'blankiliner,`asf the 'case fmay be, prior to perforatingsaidcasing or`linerby'conventional gun perfora-4 The l jelly-like materialdrilling-fluids from theV tors Or punch-*type perforator's.` displacesVand/Or excludes norma-l interval to be perforated during'theperforating procedure "and subsequent'routine completion operationsuntil efforts are made to establish ovv from the formation into thevWell bore lto determine and te's'tthe fluid contentv of the formation.Thus to accomplish this objective the material located 'in the casing,tof befperforated must be more dense 'and/or 'more viscous.' than thedrilling vfluid l i have any' plugging effect or 'when'n contact withbeing employed "and must 'not' during the perforating procedureformationrlidsfand it must `have the property of being easily removed"to 'permitsubsequent'production of oil or' gas.

The present 'invention will bef-furtherV illustrated lby'j referenceftovthe-drawing'invwhichzthe singlegure illus-y trates the steps-of apreferred mode.

Referringnow tothe drawinginumeral 11 tdes'ignates" a well bore inwhichaby ashea'th of cement with -a casing seat 14 cement 15.

casing 1'2is arranged and sealed V13. lThe 'casing 12 is'provided atits. lowerendand sealedolf by) It is *contemplated"that'cementl mayyhave been removed from 'the casing '12 vexc'eptfor the sea1'15" bydrilling out;

is filled "With"drillin`g mudiridicatedby'numeral' 16 vand 3 likewisethe tubing 17 or drill pipe is also lled with drilling mud. It will benoted that the casing 12 traverses a formation A from which productionis desired. Ordinarily the tubing string 17 or drill pipe would beremoved and the interval designated by A of the.

producing formation would then be perforated. Prior to the presentinvention a well such as 11 would be held under control where theformation pressure was high by maintaining the column of drilling mud 16in the well. Prior to the present invention, when the casing wasperforated the drilling mud would How into the perforations and resultin plugging thereof.

Accordingly in my invention in step 2 thereof, as shown in the drawing,a portion of the drilling mud 16 in the casing 12 is replaced by a bodyof a heavy and/ or viscous fluid which is characterized by the propertyof not being displaced by the drilling mud. This material may be termeda gel and is shown as a body extending 50 to 500 feet beyond the limitsof the formation A. This body of gel is indicated generally by numeral18. The gel is arranged in the well casing 12 by pumping it down thetubing 17 or drill pipe which may be lled with the gel or which may haveanother fluid above the column tig gel which remains in the tubing 17above the body After the body 18 of gel has been located in theproducing formation to form a zone or area encompassing or enclosing thearea in the casing 12 traversing the formation A, the tubing string 17may be removed and a perforator, such as a gun or shaped chargeperforator 22, or similar device on a wire line 19 or electric cable islowered in the casing 12. The shaped charge perforator 22 which is wellknown to the art is then fired to cause a jet or jets of molten metal tobe jetted through the casing 12 to form perforations 20 in the casing 12and to extend into the formation A as in 21. By virtue of firing thecharges in the shaped charge perforator 22 the gel 18 in the casing 12ows through the perforations 20 and into the fractures or cavity 21 thusexcluding or preventing any drilling mud from owing through theperforations or into the fractures or openings caused by the shooting ofthe gun perforator and the like. Thereafter the drilling mud 16 abovethe body of gel 18 is circulated out of the hole as is well knowntechnique and any gel which remains in the fractures 21 or theperforations 20 will within about 24 hours re- Vert to its componentparts of a less viscous nature than the gel and will be circulatedout ofthe fracture by production from formation A.

As shown in step 4 of my invention the tubing 17 is then lowered backinto the casing 12 and production obtained up the tubing string 17; theflow from the fractures 21 is indicated generally by the arrows.

Thus in accordance with the present invention, it will be clear that Ihave devised a simple, readily adaptable process wherein plugging ofperforations is eliminated by excluding from the zone in whichperforating operations are conducted in a casing the drilling mud whichis employed to control a well and replacing the drilling mud by amaterial which is characterized by not forming plugs and being easilyremoved.

The nature and objects of the present invention having been completelydescribed and illustrated, what I wish to claim as new and useful and tosecure by Letters Patent is:

1. A method for completing a well traversing a producing formation'whilemaintaining said well under control with a fluid column having ahydrostatic pressure in excess of the formation pressure which comprisesdisplacing only a portion of drilling iluid in a well casing to beperforated with a clean liquid having a weight in the range between 9and 18 pounds per gallon, said liquid being heavier .than the drillingfluid, inserting a casing perforator into the liquid, and perforatingthe casing in the liquid, said liquid being free of materials whichmight plug the perforations.

2. A method for completing a well traversing a proweight in the rangebetween 9 and 18 pounds per gallon and a viscosity in the range betweenand 4,000 centipoises at 60 F., said liquid being heavier than thedrilling uid and being capable of reverting to a liquid of reducedviscosity after a period of time at least 4 hours in the well, insertinga casing perforator into the liquid, and perforating the-casing in theliquid, said liquid being free of materials which might plug theperforations in said casing.

i to be perforated with a high viscosity liquid, said liquid 3. A methodfor completing a well traversing a producing formation while maintainingsaid Well under control with a lluid column having a hydrostaticpressure in excess of the formation pressure which comprises displacingonly a portion of drilling liuid in a well casing to be perforated witha clean, high viscosity, gelled liquid, said liquid being heavier thanthe drilling lluid and being capable of reverting to a liquid of reducedviscosity after a period of time in the well, inserting a casingperforator into the gelled liquid, and perforating the casing in thegelled liquid, said liquid being free of materials which might plug theperforations in said casing.

4. A method for completing a well traversing a producing formation Whilemaintaining said well under control with a iluid column having ahydrostatic pressure in excess of the formation pressure which comprisesdisplacing only a portion of drilling uid in a well casing to beperforated with a clean, high viscosity, gelled liquid, said liquidbeing heavier than the drilling iluid and being capable of reverting toa liquid of reduced viscosity after a period of time at least 4 hours inthe well, inserting a casing perforator into the gelled liquid,perforating the casing in the gelled liquid, and producing said wellfrom the producing formation through the perforated casing,

said liquid being free of materials which might plug the perforations insaid casing.

5. A method for completing a Well traversing a producing formation whilemaintaining said well under control with a iiuid column having ahydrostatic pressure in excess of the formation pressure which comprisesdisplacing only a portion of drilling fluid in a well casing to beperforated with a clean, high viscosity gelled liquid, said liquid beingheavier than the drilling fluid and being capable of reverting to aliquid of reduced viscosity after a period of time at least four hoursin the Well, inserting a gun perforator into the gelled liquid,perforating the casing in the gelledliquid by shooting said gunperforator, and producing said well from the producing formation throughthe perforated casing, said liquid being free of materials which mightplug the perforations in said casing.

6. A method for completing a Well traversing a producing formation whilemaintaining said well under control With a iiuid column having ahydrostatic pressure in excess of the formation pressure whichcomprises'dis-4 placing only a portion of drilling lluid in a wellcasing to be perforated with a clean, acid gel liquid, said liquid beingheavier than the drilling fluid and being capable of reverting to aliquid of reduced viscosity after a period of time at least four hoursin the well, inserting a casing gun perforator into the gelled liquid,perforating the casing in the gelled liquid by shooting said gun perlforator, and producing said well from the producing formation throughthe perforated casing, said liquid being free of materials which mightplug the perforations in said casing.

7. A method for completing a well traversing a prov ducing formationwhile maintaining said well under control with a fluid column having ahydrostatic pressure in excess of the formation pressure which comprisesdisplacing only a portion of drilling uid in a well casing adjacent thepoint where said well traverses said producing formation with a clean,viscous liquid having a weight in the range between 9 and 18 pounds pergallon and a viscosity in the range between l0 and 4,000 centipoises at60 F., said liquid being heavier than the drilling fluid and beingcapable of reverting to a liquid of reduced viscosity after a period oftime at least four hours in the well, inserting a casing gun perforatorinto the liquid, ring said gun perforator to form perforations in saidcasing, removing the liquid from the casing, and producing said wellfrom the producing formation through the perforated casing, said liquidbeing free of materials which might plug the perforations in saidcasing.

8. A method in accordance with claim 7 in which the liquid is an acidgel.

9. A method in accordance with claim 7 in which the liquid is a gelledliquid.

10. A method for completing a well traversing a producing formationWhile maintaining said well under control with a fluid column having ahydrostatic pressure in excess of the formation pressure which comprisesdisplacing only a portion of drilling uid in a well casing beingheavier-than and having the property of excluding drilfling Huid rcm theare.1 of fthe well casing o b References Cited in the file of thispatent per orated an eing capa e o reverting to a iqui of reducedviscosity after a period of time in the UNITED STATESPATENTS well,inserting a casing perforator in the liquid, and Number Name Dateperforating the casing in the liquid, said liquid being 5 2,316,596Kennedy Apr. 13, 1943 easily removable from the perforations in saidcasing and 2,379,516 Garrison July 3, 1945 from the formation withoutforming plugs in the per- 2,494,256 Muskat et al Jan. 10, 1950 forationsand formation. 2,530,966 Huber Nov. 21, 1950 2,596,137 Fast May 13, 195210 2,596,844 Clark May 13, 1952

1. A METHOD FOR COMPLETING A WELL TRAVERSING A PRODUCING FORMATION WHILEMAINTAINING SAID WELL UNDER CONTROL WITH A FLUID COLUMN HAVING AHYDROSTATIC PRESSURE IN EXCESS OF THE FORMATION PRESSURE WHICH COMPRISESDISPLACING ONLY A PORTION OF DRILL FLUID IN A WELL CASING TO BEPERFORATED WITH A CLEAN LIQUID HAVING A WEIGHT IN THE RANGE